added config for tap device

vpngen/default/clients/client.conf

 remote ${hostname} ${port}
 resolv-retry infinite
 cipher AES-256-CBC
+lladdr ${mac}
+ifconfig-noexec
 
 # Keys
 ca ca-${name}.crt

vpngen/vpngen.json

     "hostname": "vpn.example.com",
     "net": "10.0.0.0",
     "mask": "255.255.255.0",
+    "mac": "16:99:45:00:00:00",
     "dev": "tap",
     "user": "root",
     "group": "root",